According to the operative characteristics

the stimulated site and the curative effect-emerged site of bloodletting therapy

its clinical characteristics may be divided into three categories: a) local stimulation induced focus-local effect

b) local stimulation induced effect of the distal target organ(point-to-point distal effect)

and c) special point stimulation induced broader effect of the whole body. Accordingly

the underlying mechanisms of clinical outcomes mainly involve the improvement of the local microcirculation and secondary changes of inflammatory substances for the first category(local focus). The point-to-point distal effect might mainly involve the innervation of nerve segments

while the broad effect of specific acupoint stimulation might involve multiple levels of the neuro-endocrine-immune system. The future research on the mechanisms of bloodletting should starts from its specific effects and the type of disease

which should not be generalized.